1. Field of the Invention
The present invention relates to electric power tools. More particularly, the present invention relates to an electric power tool which has a split two-part housing for encasing a drive unit that includes a motor and a reduction mechanism for transmitting the rotation of the motor to a spindle protruding toward the top end of the tool.
2. Description of the Related Art
Various power screwdrivers and screwdriver/drills have been known in the art, as disclosed in Japan Published Examined Patent Application Nos. S59-52298 and H4-59112, both of which include a description of a split two-part housing made of synthetic resin that encloses a drive unit. Furthermore, the drive unit includes a motor and a reduction mechanism which is coupled to the motor by means of screws and transmits the rotation of the motor to a spindle protruding toward the top end of the housing. Additionally, a torque setting adjuster and a chuck are mounted on the part of the spindle protruding from the front of the housing.
When this arrangement is applied to an electric power screwdriver as in the above examples, the tool is subjected to a large force acting in the axial direction of the spindle when the tool bit is pressed against a screw or other workpiece. The split two-part housing made of synthetic resin sometimes fails to withstand the force, with the result being that the spindle and the housing become distorted or warped. This may in turn adversely affect gear engagement in the reduction mechanism and thus normal rotation of the spindle.